It should work if you supply the full path for the ffmpeg and avconv commands. You can get this by running which, e.g., which ffmpeg.
I don't have either of those programs installed on my server but I suspect that avconv is in the PATH used by cron while ffmpeg isn't.

It could be leading to the solution that a domain member should not have more than 5 minutes clock skew. See http://download1.beyondtrust.com/Technical-Support/Downloads/files/pbiso/Manuals/likewise-open-54-guide.html#id2944830
I suggest the settings of Likewise make sure that this time difference cannot occur.
A windows domain member would normally sync ...

actually, yes it is possible.
do your normal rsyncscript.sh
you will need to generate keys using the command ssh-keygen
in your home directory, go to .ssh/id_rsa.pub and copy that into the other servers /authorized_keys file

The best option, if you can, is to set up key-based SSH authentication on the remote server, and use a key with no passphrase on the client. This will allow the SSH connection, which rsync uses when you use that [user@]server:path notation, to happen without prompting for a password.
Ubuntu documentation for doing this is at:
...

Another solution is to use the recipient_canonical_maps configuration parameter of postfix. Compared to the virtual_alias_maps, the advantage is that myorigin neither needs to be in mydestination nor in virtual_mailbox_maps (which virtual_alias_domains defaults to). Thus, this postfix instance does not become the final destination for myorigin.
Add this to ...

For livestreams I would recommend using livestreamer instead of VLC. Recording with livestreamer is a breeze, e.g.:
livestreamer <livestream-url> best -o vod.mp4
livestreamer supports dozens of different streaming providers and works very reliably, even with spotty streams.
For installation instructions check out this answer by @henry.

Looks like it can't create the log file. Check the permissions of /var/log folder. It should be
ls -l /var/
drwxrwxr-x 18 root syslog 4096 Mar 6 14:30 log
If it doesn't look like the first starting with the drwxrwxr-x, change the permissions to the folder by typing in the following:
sudo chmod 775 /var/log
Run the cron job again.

The crontab file is indeed provided by the cron package. This package is installed by default (See the 12.04 Manifest).
The crontab command should already be in your $PATH:
$ type crontab
crontab is /usr/bin/crontab
Check the Official documentation to know how to set up your crontab.

Cron will simply execute all lines sequentially. It won't wait for one to exit to launch another. There might be a maximum limit but I doubt it, if you launch too many resource intensive processes, you'll just crash your machine just like you would if you'd run them manually.
If you have enough processes so that the time it takes to launch them all is more ...